The present invention relates to monitoring the wheel slip of a plurality of wheels of a vehicle, such as a truck (e.g., a heavy duty or medium duty truck) and/or a heavy duty truck tractor (e.g., a heavy duty or medium duty truck) and trailer combination and determining brake problems and evaluating brake performance from this monitoring.
ABS brake systems are known in which a wheel sensor is provided for each wheel of the vehicle which is to be monitored, typically one wheel speed sensor per vehicle wheel. The ABS brake systems typically compare the speed of each wheel to the vehicle speed and if there is significant slippage (e.g. a wheel speed varies more than 10 to 15 percent from the vehicle speed), the ABS system is operated. That is, if the wheel starts slipping beyond these significant limits, the brake for the slipping wheel or wheels is released.
Minor braking incidences of a vehicle can also produce a small amount of wheel slip. However, known ABS systems ignore minor wheel slip information.
A need exists for an improved brake monitoring system.
In accordance with the invention, wheel slippage below that which triggers the operation of an ABS system is monitored. In particular, wheel slippage in the range of from about 0.1 percent to 2 percent is monitored. Changes in wheel slippage of a specific wheel at these minor slippage levels over time indicate possible problems with the wheel, such as in the bearings or brakes of the wheel. From changes in wheel slippage information from one braking incident to another for a particular wheel and from comparing wheel slippage of each wheel to that of the other wheels, a determination can be made of the nature of the problem and whether maintenance should be undertaken. Information can be displayed to the driver as well as transmitted remotely for use by a dispatcher in determining the potential significance of the problem. A dispatcher may then determine whether, for example, immediate maintenance should be undertaken or whether maintenance may be delayed until a subsequent scheduled maintenance time. In addition, an alarm indicator may be activated, with selective activation being a possibility, to indicate to a mechanic or a vehicle inspector, for example, that there is a problem with a wheel of the vehicle.